1. Field of the Invention
The present invention relates to a magnesium alloy for high pressure casting including a process for the preparation thereof, and more particularly to a magnesium-based alloy containing aluminum, zinc, silicon etc. in combination with phosphorus and copper for improving the strength and toughness thereof. Advantageously, the alloy of the present invention is used in a die-casting or squeeze-casting process.
2. Description of the Related Art
Various types of magnesium-based alloys are known in the art. Generally, magnesium-based alloys possess excellent strength and light weight and are used for regular casting and high pressure casting. Accordingly, the product made with magnesium-based alloys have been used in automobile parts and airplane parts.
Such conventional magnesium-based alloys contain, for example, 8.3-9.7 weight percent (hereinafter "W %") of aluminum, 0.35-1.0 W % of zinc, less than 0.15 W % of Manganese, less than 0.1 W % of silicon, and the remainder being magnesium; 5.5-6.5 W % aluminum, less than 0.22 W % of zinc, greater than 0.13 W % of manganese, less than 0.5 W % of silicon, and the remainder being magnesium; and 3.5-5.0 W % of aluminum, less than 0.12 W % of zinc, 0.2-0.5 W % of manganese, 0.5-1.5 W % of silicon and the remainder being magnesium. Such conventional magnesium-based alloys are satisfied with less than 0.005 W % of iron, less than 0.03 W % of copper, and less than 0.002 W % of nickel.
Also, U.S. Pat. No. 5,078,962 discloses high mechanical strength magnesium alloys and a process for manufacturing the same by rapid solidification and consolidation by drawing, generally exceeding 400 or 500 MPa, with an elongation at break of at least 5%. These alloys have a chemical composition of 2-11 W % of aluminum, 0-12 W % of zinc, 0-1 W % of manganese, and 0.1-4 W % of rare earth elements, with the main impurities and residue being magnesium.
However, these conventional magnesium-based alloys suffer from a number of problems such as, for example, they have a low strength when subjected to high elongation, they have a low elongation if they have high strength, and thus they do not have high strength and elongation.